40 storey office tower is a hybrid of concrete and wood
The concrete industry is getting all shirty about the current interest in wood as a construction material for mid rise buildings. But there is no question that there are a lot of advantages to wood: we have lots of it, much of it is dying right now due to pine beetle infestation, it is renewable, and it stores carbon dioxide. Concrete, on the other hand, is made by cooking the CO2 out of limestone and mixing it with huge amounts of rock dug out of big holes in the ground.
But concrete has real advantages too. Perhaps instead of fighting wood, the concrete people should be asking "why can't we just get along?"
An example might be this "Office Building of the Future", a runner-up in a NAIOP ideas competition. It's designed by CEI Architecture of Vancouver. It's a hybrid, a mix of wood and concrete that lets the two materials get along by picking and mixing the best attributes of both. Wood doesn't have the compressive strength to go 40 storeys high, but concrete does it all the time.
The architects write in Construction Business Magazine
A smart alternative is to combine wood with other materials in a hybrid fashion, minimizing concrete and steel as the primary support and emphasizing wood for secondary structural systems. With this in mind, the goal was to maximize the use of wood and propose innovative systems as a commitment to environmental sustainability.
The scheme proposes a building footprint of 150 feet by 90 feet, with a central concrete core. Floor decks are made of wood-concrete composite elements that take advantage of the superior tension quality of wood and the compression capacity of concrete. The choice of composite also has acoustic benefits. Floors are constructed of CREE panels spanning 30 feet from the core to the perimeter truss.
CREE panels are an Austrian design of hybrid panels seen on TreeHugger here.
Four concrete piers 30 feet from the end are strategically positioned at building perimeters to support the wood trusses with cantilevers to achieve further structural efficiency. Reinforced concrete is used for its structural properties of strength, rigidity, ductility and continuity, to resist lateral forces such as earthquakes and wind.
In the end, it is the best of both worlds. The design uses concrete where it is clearly the best material for the job, and wood for the rest.
The concrete industry should be promoting this kind of thing, not fighting it.